Many Radio Frequency Identification (RF-ID) applications require the use of a multitude of transponders in any given interrogation read range. For example, manufacturing applications of RF-ID systems, where thousands of items must be tracked, thousands of transponders are located throughout the warehouse. Therefore, the more large an area within which transponders are to be read, the higher the probability that some kind of noise will interfere with the transponder response signal, thereby making identification of the tracked part ineffective.
In addition, in many industrial applications, where different electrical or electronic devices are located nearby transponders to be read, the devices may generate different kinds of noise. Under these environmental conditions, RF-ID systems are especially adversely affected by the generated noise. White noise or low level noise is always existing from lights, or any other continuously running electronic mechanisms i.e. refrigerators, computers etc., but is generally compensated for in the robustness of the system. Another kind of noise generated by these nearby electronic devices are voltage spikes, in the air or on AC lines, generated by the switching on and off of the different electronic devices. Under these conditions, the ID system does not receive valid data from the transponders because a few bits of the transponder response signal are partly corrupted by a spike although the rest of the response signal is uncorrupted. This kind of noise may deteriorate the performance of the system up to 20-30 percent of the ideal performance.